The present invention is a device for rapid and unambiguous troubleshooting of the idle speed control circuit in a computer controlled automobile engine.
Miniature computers are widely used to control many functions in automobile engines. One function is to control the engine idle speed based upon temperature, air conditioner load, shift lever position, and difficult The engine frequently stalls and then the function cannot be tested. In the prior art, four troubleshooting methods were commonly used:
1. Parts replacement. PA0 2. Engine data Mini Scanners. PA0 3. Trouble shooting procedures. PA0 4. Kits of test wires.
In the first method the mechanic merely continues replacing parts until the problem is solved. Obviously an expensive and unsatisfactory method.
The second method is to use an engine data Mini Scanner. These scanners are available from several companies. ALLTEST Model 3258 (prior art reference AT) and OTC No. 213481 (prior art reference AY) are examples of engine data Mini Scanners. The scanners display a number from the computer which is a numerical representation of the idle speed control output of the computer. However, the number thus displayed only shows a number from the variable memory inside the automobile computer. The speed control number does not necessarily represent the output signal to the idle speed control stepper motor. Also, the scanner cannot directly display the action of the stepper motor itself. The scanner indirectly shows the stepper motor action by displaying the engine RPM. This indirect display leads to ambiguities in trouble shooting, since other engine parts can cause idle speed problems.
The third method involves complicated trouble shooting procedures which are printed in various manuals and handbooks (prior art references AX and AY). A good example of the confusing procedures is page 387 in "Tools and Techniques Book" (reference AX).
The fourth method involves kits of test wires. Some kits are made by the mechanic, and some are sold by test equipment manufacturers Kits 3456 and 3458 on page 33 of prior art reference AW are two examples. Usage of kit 3456 or 3468 shown is likely to result in mistaken connections which may destroy the computer or the idle speed control stepper motor.
A review of the current manufacturers catalogs and literature (prior art documents AR thru BC) has not revealed any test equipment which even remotely resembles that disclosed in this application. Applicant is not aware of any other test equipment or methods for troubleshooting an automobile engine idle speed control circuit.
It would therefore be an advance in the art to provide test equipment which would enable the mechanic to rapidly and unambiguously determine which element of the idle speed control circuit is defective. This application describes such test equipment.